1、 ISO 2014 Timber structures Strength graded timber Test methods for structural properties Structure en bois Bois class selon la rsistance Mthodes dessai des proprits structurelles INTERNATIONAL STANDARD ISO 13910 Second edition 2014-05-01 Reference number ISO 13910:2014(E) ISO 13910:2014(E)ii ISO 20
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4、d in Switzerland ISO 13910:2014(E) ISO 2014 All rights reserved iii Contents Page Foreword iv Introduction v 1 Scope . 1 2 T erms and definitions . 1 3 Symbols and abbreviated terms . 2 3.1 General notation 2 3.2 Subscripts 3 4 Test specimens 3 5 Test conditions . 3 6 T est c onfigur ations . 3 6.1
5、Density . 3 6.2 Bending strength and stiffness . 4 6.3 Tension strength parallel to the grain . 5 6.4 Compression strength parallel to the grain . . 6 6.5 Shear strength parallel to the grain 7 6.6 Tension strength perpendicular to the grain 9 6.7 Compression strength and stiffness perpendicular to
6、the grain 11 6.8 Torsional shear modulus .13 7 Adjustment for non-reference test conditions .14 8 Test report 15 Annex A (informative) Adjustment factors for non-reference condition 16 Bibliography .17 ISO 13910:2014(E) Foreword ISO (the International Organization for Standardization) is a worldwide
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11、e document will be in the Introduction and/or on the ISO list of patent declarations received. www.iso.org/patents Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanation on the meaning of ISO specific terms an
12、d expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT), see the following URL: Foreword - Supplementary information The committee responsible for this document is ISO/TC 165 Timber Structures. This se
13、cond edition cancels and replaces the first edition (ISO 13910:2005), which has been technically revised.iv ISO 2014 All rights reserved ISO 13910:2014(E) Introduction This International Standard provides requirements for testing of structural properties for a specific grade and size of sawn timber.
14、 In accordance with the requirements of performance-based International Standards, it is concerned with the measurement of properties similar to those that occur under service conditions and are intended for deriving engineering properties in structural design codes. Hence, terms such as “bending st
15、rength”, “shear strength”, “bearing strength”, etc. relate to the loading configuration used and to the targeted mode of failure. It is not the intent to imply that every property of every grade and size of timber used in building construction needs to be assessed according to this International Sta
16、ndard. The requirements for any assessment typically are specified in building regulations, quality manuals or other material standards and specifications. This document is an internationally-agreed reference standard for measurement of structural properties of strength-graded timber. Other standard
17、s related to the measurement of structural properties may be deemed to comply with this International Standard, provided that the adjustments necessary to establish equivalency between this and other standards are applied appropriately ISO 2014 All rights reserved v Timber structures Strength graded
18、 timber Test methods for structural properties 1 Scope This International Standard specifies test procedures for full-size sawn timber that has been strength- graded, for the derivation of design properties in codes dealing with structural engineering design. It is applicable to sawn timber of recta
19、ngular cross-section subjected to a short-duration load. 2 T erms a nd definiti ons For the purposes of this document, the following terms and definitions apply. 2.1 grade population of timber with defined design properties in a design standard 2.2 piece of timber timber of rectangular cross-section
20、 manufactured for construction purposes of a specific grade 2.3 test specimen length of timber, cut from a piece, for purposes of testing to evaluate a timber property INTERNATIONAL ST ANDARD ISO 13910:2014(E) ISO 2014 All rights reserved 1 ISO 13910:2014(E) 3 Symbols and abbreviated terms 3.1 Gener
21、al notation a distance between a load point and nearest support in a bending test set-up, expressed in mm b thickness (smaller dimension of a cross section) of a rectangular piece or specimen of tim- ber, expressed in mm E modulus of elasticity parallel to direction of grain, expressed in MPa F appl
22、ied load, expressed in N f strength, expressed in MPa G shear modulus of rigidity, expressed in MPa h width (larger dimension of a cross section) of a rectangular piece or specimen of timber, expressed in mm K stiffness, expressed in N per mm deformation L length along a piece or specimen of timber,
23、 expressed in mm L T length of test specimen subjected to torsion forces, expressed in mm l h length cut from a specimen, expressed in mm l t lever arm of applied torsion load, expressed in mm e displacement of beam, expressed in mm m mass of specimen, expressed in kg SH v volumetric shrinkage of wo
24、od from green fibre saturation point (FSP) to oven-dry condition w ratio of mass of water to mass of oven-dry wood, equivalent to moisture content w FSP moisture content at fibre saturation point x i data value rotational deformation in a torsion test, in radians density, expressed in kg/m 3 12 dens
25、ity, expressed in kg/m 3 , at 12% moisture content test density, expressed in kg/m 3 , at time of test2 ISO 2014 All rights reserved ISO 13910:2014(E) 3.2 Subscripts 0.1h value at deformation of 0.1h 0 property in a direction of 0 to the grain 90 property in a direction of 90 to the grain c compress
26、ion m bending t tension ult value at failure v shear 4 Test specimens All test specimens are of full-size cross section. The length required for a test specimen shall be related to the specific test (see Clause 6). Unless otherwise stated, test specimens shall be selected from random locations withi
27、n a piece of timber. Specimens cut from pre-defined locations (centre of a piece of timber, a randomly selected end within a piece or clear sections, etc.) may be deemed to comply with this requirement provided this does not produce any bias in the measured properties. Each test specimen for a given
28、 size, grade or property shall be cut from a different piece of timber and more than one type of test specimen may be cut from each piece. 5 Test conditions Unless otherwise specified in the description of the reference population, the reference moisture content at the time of testing shall be consi
29、stent with conditioning at a temperature of 20C (2C) and 65 % (5 %) relative humidity. Other test procedures and conditioning criteria may be used provided they are more conservative; otherwise, an equivalency in performance for these alternative procedures and conditions shall be established. The r
30、ate of loading shall be selected that targets average time-to-failure in 1 min to 5 min. NOTE The intent here is not to reject data for weak pieces that fail in a short time. At the time of testing, the moisture content of the timber, the temperature of the timber, and the time to failure shall be r
31、ecorded. 6 T est c onfigur ation s 6.1 Density The specimens for the measurement of density shall be free of knots and comprise the full cross-section of the piece of timber. The length of the test specimen shall be a minimum of 50 mm. The mass, m, and ISO 2014 All rights reserved 3 ISO 13910:2014(E
32、) moisture content, w, are measured for each test specimen. The density at the time of test, test , shall be calculated from (1) The density at 12 % moisture content, 12 , shall be calculated from w (2) where w is the moisture content at the time of test as determined by the oven-dry method. Alterna
33、tively, it may be sufficiently accurate to measure moisture content by means of a moisture meter, provided that the meter is calibrated against moisture content measurements determined by the oven dry method. Where such moisture meter measurements are made, they shall be made at several locations al
34、ong each specimen. NOTE If specific gravity (e.g. based on oven-dry mass and oven-dry volume, SG OD ) is desired, it can be estimated from wood density at test, test , moisture content, w, fibre saturation point, w FSP , and wood volumetric shrinkage, SH v , as follows: 6.2 Bending strength and stif
35、fness The bending strength and stiffness test configuration shall be as shown in Figure 1. The beam specimen shall be loaded at two points, equally spaced between the end supports, with each load equal to F/2. The distance between load points shall be 6 h and the distance between a load point and th
36、e nearest support, a, shall be 4,5 h to 7 h. The tension edge of the beam shall be chosen randomly. If the beam has a slenderness where there could be a tendency for the compression edge to buckle during loading, lateral restraints may be provided to the compression edge. Such restraints shall not r
37、esist any movement in the direction of the loading. Bearing blocks at loading and support points (see Figure 1), shall be of sufficient thickness and extend entirely across the beam thickness to eliminate high-stress concentrations at places of contact between beam and bearing blocks. Load shall be
38、applied to the blocks in such a manner that the blocks may rotate about an axis perpendicular to the span. The slider bearing plate in Figure 1 shall allow rotation and horizontal movement whereas the bearing plate shall allow only rotation. F/2 F/2 a a L h b A B C e 1 1 1 2 Key 1 slider bearing pla
39、te 2 bearing plate (rocker) Figure 1 Test set-up for measuring bending strength and stiffness4 ISO 2014 All rights reserved ISO 13910:2014(E) Modulus of elasticity, E, shall be calculated from measurement of e, the centre-point deflection of the centre-line of the beam relative to the position of th
40、e centre-line at the ends of the beam, i.e. the deflection of point B relative to points A and C as shown in Figure 1. NOTE Centre-point deflection measured by referencing the displacement transducer against the top or bottom edge of the beam or by using loading head movement usually contains uninte
41、nded displacement component due to the indentation of the wood material at the support and loading points, etc. Deflection measured by such methods can be used for calculation of E provided it can be shown that it leads to more conservative result. The applied load, F, shall be increased until the m
42、aximum load is reached. To evaluate the modulus of elasticity in bending, E m , the incremental deflection e for an incremental load F shall be selected from the linear elastic part of the load-deformation graph. E mis calculated from: (3) The range of 10 % to 40 % of the maximum load shall be used
43、to determine F/e. The deflection e may be evaluated by the measurement of the movement of points other than those described above, provided that an acceptable equivalency for these procedures is established, or it can be shown that the alternative procedures produce conservative results. NOTE The te
44、st set-up will lead to the determination of apparent modulus of elasticity. Shear-corrected modulus of elasticity can be estimated by adjusting the measured deflection, s, using the following formula assuming shear modulus is known (For structural timber, G can be assumed to be E /16.), and substitu
45、ting e into Formula (3): 1 The bending strength, f m , shall be calculated from (4) where F ultis the value of the applied load at failure. 6.3 Tension strength parallel to the grain NOTE The gauge length used is typically longer than the stated minimum to increase the likelihood that the critical s
46、trength-reducing defect is captured within the gauge length. F F h Gauge length 1 1 b Key 1 grip Figure 2 Test setup for measuring tension strength parallel to the grain ISO 2014 All rights reserved 5 ISO 13910:2014(E) The tension strength f t,0shall be calculated from (5) where F ultis the value of
47、 the applied load at failure. 6.4 Compression strength parallel to the grain The compression strength parallel to the grain test configuration shall be as shown in Figure 3. The test specimen shall be the full length of the piece of timber. It shall be compressed axially by a load F until failure oc
48、curs. The specimen should be restrained against lateral buckling with the spacing of the lateral restraints not greater than 5h for buckling about the major axis and 5b for buckling about the minor axis. The lateral restraint shall not provide any resistance in the direction of the loading. b h F F 1 1 5h 5b Key 1 lateral restraint Figure 3 Test setup for measuring compression strength parallel to the grain using the full length test specimen The compression strength f c,0shall be calculated from (6) where F ultis the value of the applied load at failure. An alternat
